Tank volume and capacity guide
Calculate ideal internal volume and liquid capacity for rectangular, vertical cylindrical or spherical tanks.
Use consistent internal dimensions and verify product, supplier and project requirements before relying on the purchasing result.
How to use this calculator
- Select the calculation: Choose the applicable shape and unit system.
- Measure the scope: Enter finished internal or installed dimensions as labeled.
- Review assumptions: Confirm allowance, packaging, fill or product inputs where applicable.
- Verify the result: Compare the result with project documents and current supplier information.
Formula and variables
Ideal internal cubic volume is converted to liters and US gallons, then multiplied by fill percentage.
Rectangle = L × W × H; cylinder = πr²h; sphere = 4πr³ ÷ 3- Dimensions — Measured geometry
- Positive dimensions entered in the displayed units.
Worked example
A metric cylinder is 1 m in diameter and 2 m high.
- Project geometry
- As described in the example
- Rectangle = L × W × H; cylinder = πr²h; sphere = 4πr³ ÷ 3
- Ideal internal cubic volume is converted to liters and US gallons, then multiplied by fill percentage.
Result: Full capacity is approximately 1,570.8 liters.
Treat the result as a transparent planning quantity, not a design approval or supplier guarantee.
Understanding your results
Calculated quantity
The formula result before product-specific adjustments unless stated.
Purchasing result
A rounded or adjusted quantity based on the entered planning assumptions.
Assumptions
- Dimensions are internal.
- The tank matches the selected ideal shape.
Limitations
- Heads, wall thickness and fittings are excluded.
- Horizontal partial-cylinder fill is not modeled.
Common mistakes
- Using external dimensions.
- Confusing radius and diameter.
- Treating nominal capacity as usable capacity.
Practical use cases
Preliminary takeoff
Create a transparent quantity for scope and budget review.
Supplier discussion
Bring dimensions and assumptions to confirm product quantities and rounding.
Planning and decision guide
Measure consistently
Record measurement boundaries and units so the estimate can be reproduced.
Confirm current requirements
Use approved project documents and current manufacturer or supplier information.
Frequently asked questions
Is this result exact?
It is exact for the entered idealized geometry, but field conditions and product rules can change the practical quantity.
Can I mix units?
No. Enter every dimension using the units shown for the selected system.
Does this replace project design?
No. It is a planning calculation only.
Sources and review
- NIST Handbook 44: Liquid-Measuring Devices — National Institute of Standards and Technology. Accessed 2026-08-03.
Reviewed 2026-08-03.